This invention relates to a moisture drain bush for an engine starter motor and, more particularly, to a moisture drain bush adapted to be inserted into and held by a moisture drain hole defined in a housing wall of an engine starter motor.
FIG. 1 illustrates one example of a conventional moisture drain bush attached to an engine starter motor. In FIG. 1, a starter motor 1 comprises a d.c. motor 2, an over-running clutch unit with a pinion (not shown) disposed within a front bracket 3 and a solenoid switch unit 4 disposed above the motor 2 and the clutch unit. The d.c. motor 2 includes a yoke 5 and a rear bracket 6 mounted to the yoke 5 for rotatably supporting a rear end of a rotary shaft 8 of the motor 2 through a bearing 7. The motor 2 further includes a commutator 9 which is in sliding contact with a brush assembly 10 supported from the rear bracket 6. The rear bracket 6 has formed therein a moisture drain hole 11 in which a moisture drain bush 12 is inserted and held.
In FIGS. 2 and 3, which illustrate the details of the drain bush 12, the drain bush 12 is a substantially cylindrical tube member comprising a main body 13, an upper flange 14 formed at the upper end of the mian body portion 13, a lower flange 15 disposed below the upper flange 14 with a clearance or a circumferential groove therebetween for receiving therein an edge of the rear bracket 6 defining the drain hole 11. The drain bush 12 also comprises a plurality of buffer plates 16 extending radially inwardly and downwardly and alternatively from the diametrically opposite inner surfaces of the tube so that a ladyrinth or a serpentine flow path is defined. The upper flange 14 has formed therein two radially extending notches 14a.
The moisture within the motor housing flows through the drain notches 14a into the drain bush main body portion 13 and flows out from the bottom end of the drain bush 12. The splashed water drops entering into the drain bush 12 from its bottom end are prevented by the buffle plates 16 from passing through the drain bush 12 and entering into the interior of the motor housing.
With the above described conventional moisture drain bush, the drain bush 12 is projecting from the rear bracket 6 by a substantial outwardly distance. Therefore, the degree of freedom of the installation of the starter motor is limitted and some mounting space is occuppied by the projecting drain bush 12.